<template>
    <div>
        <p>请选择你要购买的书籍</p>
        <ul>
            <li v-for="item,index in arr" :key="index">
                <button @click="add(index)">买书</button>
                <span>{{item.name}}</span>
            </li>
        </ul>
        <table border="1" width="500" cellspacing="0">
            <tr>
                <th>序号</th>
                <th>书名</th>
                <th>单价</th>
                <th>数量</th>
                <th>合计</th>
            </tr>
            <tr v-for="item,index in arr" :key="index">
                <th>{{index}}</th>
                <th>{{item.name}}</th>
                <th>{{item.price}}</th>
                <th>{{item.count}}</th>
                <th>{{item.price*item.count}}</th>
            </tr>

        </table>
        <p>总价格为:{{total}} </p>
    </div>
</template>

<script>
    export default {
        data() {
            return {
                arr: [{
                        name: "水浒传",
                        price: 107,
                        count: 0,
                    },
                    {
                        name: "西游记",
                        price: 192,
                        count: 0,
                    },
                    {
                        name: "三国演义",
                        price: 219,
                        count: 0,
                    },
                    {
                        name: "红楼梦",
                        price: 178,
                        count: 0,
                    },
                ],
            };
        },
        methods: {
            add(index) {
                this.arr[index].count++
            }
        },
        computed: {
            total() {
                return this.arr.reduce((sum, obj) => sum + obj.price * obj.count, 0)
            }
        }
    };
</script>